Back in late November, Boston author Dennis Lehane was speaking to fans in Western Massachusetts when the subject of social media came up.

Mr. Lehane said he'd tried Twitter but he didn't really understand the allure. His Facebook account was primarily a venue for promoting his books.

But all that changed at Christmastime when the Lehane family's beloved beagle, Tessa, slipped out of the yard and into the wilds of Brookline. There was a Facebook post on the author's wall asking folks to keep an eye out for Tessa — and the promise that if someone found her, they'd become a character in his next book.

Then there was a Tweet. And more Facebook postings. Those were followed by a barrage of media attention, including CNN.

Now there's a community of more than 3,500 Facebook followers who spend time plastering posters to poles and scouring the streets hoping to find the elusive hound. Those too far away to join the physical search send prayers, offer tips and post on the Finding Tessa Facebook page, stories of other lost dogs found after seemingly hopeless amounts of time.

Among those offering help were the members of Granite State Dog Recovery, a nonprofit group that in January alone helped reunite 100 dogs with their owners.

The group started when a few folks who'd been deploying themselves to find missing dogs decided they could incorporate and help even more dog owners.

“And a year and a half later, we have 15,000 followers,” said Beth Corr, a member of the group's board of directors.

Granite State loans out traps and trail cameras. They help search, print posters and operate on a budget that consists only of donations. The biggest expense is gas to get them to and from searches.

Though it's named for the state of New Hampshire, Granite State Dog Recovery branches out into all of New England. The volunteers there offer tips on how to keep a dog from becoming lost, and if one does they spring into action to help find the canine.

Snoopy, a rescued beagle from Sutton, probably wouldn't have survived without the incredible exposure he got on the Internet.

“He would have died standing there,” Snoopy's owner Lynne Feiz said.

But Snoopy lived, despite having his retractable leash caught in some brush as he stood freezing in a swamp on Jan. 2.

Because he'd run off once before and been found quickly, Ms. Feiz knew she had to get the word out that Snoopy was missing after her daughter fell while walking him and he ran off. She posted on Facebook and Granite State Dog Recovery and quickly found, as she searched for the dog, that she wasn't alone.

“There were other people out there, people we didn't even know, who were out there looking,” she said. “Hundreds and maybe thousands of people saw that posting.”

And so, when a neighbor a short distance away spotted the missing dog poster on Facebook, she realized the animal sound she heard coming from the swamp near her house might have been Snoopy.

Ms. Feiz said her family traipsed into the swamp, though muck so thick their boots kept coming off. Her brother spotted Snoopy, hunkered down, cold, scared and stuck. He cut the leash with his pocket knife and they passed the dog back and forth as they alternately freed themselves from the mud.

Since then, Snoopy's been outfitted with a GPS tracking system, just in case. Ms. Feiz said she, and many others, incorrectly thought Snoopy could be tracked by the microchip implanted under his skin.

She even called the company and asked them to track the dog but learned that the chip is “really just an implanted tattoo,” and that it won't provide any information unless the dog is found and scanned.

Jennifer Cosgrove of Auburn is pretty sure her sister's dog, Mischief, wouldn't have been found without Facebook, either.

“She had stopped in to see a friend in Worcester at work for a few minutes, and she locked Mischief in the car, but the window was down just enough for someone to reach through,” Ms. Cosgrove said. “When she came back, the dog was gone and her collar was thrown in the back seat.”

The car was still locked.

The family immediately suspected the good natured gray pit bull was stolen.

Ms. Cosgrove turned to Facebook, quickly sharing pictures of the dog and the news that she was missing. They used the Granite State Dog Recovery template and posted a flier on the group's Facebook page.

Like the old shampoo commercial, two friends told two friends, and so on and so on, until people who lived hundreds of miles away were posting Mischief's picture.

Less than a day later, a man called wanting to return the dog.

“He said he'd found her running loose,” Ms. Cosgrove said, adding that while the story seemed suspect, the main objective was to get the dog back and that was accomplished.

Ms. Corr said the focus is always to get the dog back, and by posting pictures and sharing the information, either people look for and find the dog or, in the less frequent cases of stolen dogs, thieves see the posts and get uneasy.

Country singer Dierks Bentley's dog, Jake, bolted during a Tennessee thunderstorm on Jan. 13 and was found and returned after someone saw his owner's frantic Facebook posts.

“One of the happiest days of my life,” the singer wrote once Jake was home. “Grown men don't cry ... yeah, right. Thank you to everyone on Facebook and Twitter that spread the word.”

While most of the stories have happy endings, some dogs do not survive their ordeals.

There are those who wonder whether or when they should give up looking, to which Ms. Corr responds: Never.

“Never, ever, give up until you have a resolution,” she said.

Granite State has found a dog missing for two years and another, they dubbed Gypsy, was on the run for a year. Dogs, she said, are surprisingly resourceful, especially rescue dogs that have lived on the street before.

“One of the things that still amazes me is how quickly they go into flight mode,” she said of the dogs she's searched for.

The biggest threat to dogs on the run are probably cars, Ms. Corr said. There are not as many predator attacks as one would think, and traffic-savvy dogs can do okay, but dogs unfamiliar with living on the streets are more likely to be hit.

In the case of Tessa and canines like her, having been a rescue dog is both a blessing and a curse. She likely has the street smarts to survive, but that may also make her less likely to come to someone who's trying to help.

Tessa's family is hoping that if someone did take her in, they will get her to a veterinarian because she was being treated for heartworm and needs medication, something they recently revealed on their Facebook page.

Ms. Corr said many folks who aren't fans of the Internet or social media learn quite quickly that it has its good uses.

“I often wonder how people found their missing pets before,” she said.

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